What is a sine chart in math? (I'm new and only have 1 reputation. Please be very nice with me.) Hello guys, I'm just wondering, What is a sine chart in math? I've heard about these in a question and in my mind I was like "What in the world is a sine/sign chart?". Can you please help me out? Thank you to all who tries to help out. I would really appreciate it.
 A: I think you mean a sign chart, rather than a sine chart.  Sine is the name of a specific function.
So, what we mean by a sign chart is a chart that tells us where a function $f(x)$ is positive or negative.
For example, consider $f(x) = (x - 2)(x - 3)$.  This is a function.  To create a sign chart, we first find the $x$ values that make this function $0$.  That would be $x = 2$ and $x = 3$.
We mark those on a number line.  Then, for every region on the number line, we plug a test point from that region into the function, and figure out if the output number will be positive or negative.  If it is positive, then the function $f(x)$ is positive on that entire region where the test point came from.  If the output is negative, then the function $f(x)$ is negative on the entire region where the test point came from.
A: If you are referring to  the trig functions sine/cosine .. they could be graphs of projections of a point going round a point on a diameter or its perpendicular of circle described. 
